1. Field of the Invention
Exemplary aspects of the present invention generally relate to a developing unit utilized in a copier, a printer and a facsimile, or an image forming apparatus, for example, a multifunctional machine using electrophotographic method, and more particularly to a developing unit, a process cartridge and an image forming apparatus including the same.
2. Discussion of the Background
According to the related arts, in image forming apparatuses such as a copier, printer and so forth, various techniques have been proposed to prevent a developing agent or a developer stored in the developing unit from scattering out of the developing unit.
Related art developing unit storing a two-component developing agent or a developer containing non-magnetic toner and magnetic carriers have been used. An additive may be added to the two-component developer.
The developing unit may include a developing roller serving as a developer carrier, a doctor blade serving as a developer regulator, an agitation/transportation member and so forth.
Toner is supplied to the developing unit from a toner supply outlet as needed according to an amount of toner consumption in the developing unit.
The supplied toner is mixed and transported along with the developer in the developing unit by the agitation/transportation member. The part of the mixed developer is carried on a developing roller.
The developer carried on the developing roller is regulated at an appropriate amount at an opposing position or a second opposing position relative to a doctor blade.
Subsequently, the toner in the developer adheres to a latent image on a photoreceptor drum which is an image carrier at an opposing position or a first opposing position relative to the photoreceptor drum.
In such a developing unit, in order to prevent the developer in the developing unit from scattering out of the developing unit, a sealing member (i.e., an inlet sealing) is disposed upstream of the photoreceptor drum in a rotating direction thereof relative to the first opposing position, which is, the upstream position in a traveling direction of the photoreceptor drum so that the sealing member or the inlet sealing abuts along the longitudinal direction of the photoreceptor drum.
The sealing member serving as a developer dispersion prevention member and a developer accretion prevention member is formed of a flexible material such as a polyurethane rubber and is held to a holder or a supporting member through a double-sided tape.
The holder, which the sealing member is adhered to, is provided to the doctor blade or another holder holding the doctor blade. The holder is fastened by a screw or a similar structure to the doctor blade or to the holder holding the doctor blade.
The sealing member or the inlet sealing structured in a manner described above, covers the position upstream of an opening of the developing unit at the first opposing position, which is the position upstream of the photoreceptor drum in the rotating direction thereof. Additionally, a portion of the developing roller is exposed from the opening.
Therefore, an air current flowing into the developing unit along with a rotary motion of the photoreceptor drum may be shut. Furthermore, a problem of the developer dispersing out of the developing unit due to an increase of the internal pressure of the developing unit may be prevented, if not reduced.
Additionally, a technology that suctions the air in the developing unit by a pump to reduce the internal pressure of the developing unit has been proposed.
However, the related art developing units described above are not able to adequately prevent the developer from scattering out of the developing unit.
In a high-speed image forming apparatus, the rotation speed of the photoreceptor drum and the developing roller may also become high-speed. Consequently, the air current flowing into the developing unit along with the rotary motion of the photoreceptor drum may increase. The increase in the air current may also increase the chance of the dispersion of the developer occurring.
As shown in FIG. 1, when there is a small gap between the doctor blade 850 and the holder 860, the air may easily flow into the developing unit 800. Consequently, the internal pressure of the developing unit 800 may increase causing the toner or the developer to scatter.
The developer borne on the developing roller 800 may be accumulated. Thus, the accumulated developer indicated by a letter symbol G may come into contact with the surface of the holder or an inlet sealing 870. Consequently, a negative pressure may be generated in the area sealed by the developer G. As a result, the internal pressure of the developing unit increases, causing the toner or the developer to scatter.
Another related art technology that suctions the air in the developing unit by a pump to reduce the internal pressure is reduced may be expected to prevent or reduce the dispersion of the developer out of the developing unit. However, since the pump is not designed specifically to eliminate the factors that cause the increase in internal pressure of the developing unit (i.e., the internal pressure of the developing unit increases due to an enhancement of the speed of the image forming apparatus), the size of the pump needs to be increased so that the suction increases accordingly.